Flow system having electrostatic charge reducer

ABSTRACT

A FLOW SYSTEM FOR PETROLEUM PRODUCTS AND THE LIKE. AN UNSHROUDED STATIC CHARGE REDUCER TUBE IS CONNECTED IN THE STORAGE MEANS OF THE FLOW SYSTEM FOR ELIMINATING ELECTROSTATIC MEANS OF THE FLOW LIQUID FLOW. THE REDUCER IS FORMED OF A SUITABLE PLASTIC AND A PLURALITY OF PINS PROJECT INWARDLY INTO THE INTERNAL FLOW PASSAGEWAY. A CONDUCTIVE MEMBER CONNECTS THE PINS TO THE STORAGE MEANS OR SOME OTHER ELEMENT WHICH DEFINES A GROUND CONNECTION.

Nov. 2, 1971 c. D. ERICKSON ETAL 3,616,815

FLOW SYSTEM HAVING ELECTROSTATIC CHARGE REDUCER Filed June 17, 1969 INVENTORS Charlas D Erlckson Y Grzo g2 A.Ciotti 5%! 5 I I II Attorneys United States Patent ce Patented Nov. 2, 1971 3,616,815 FLOW SYSTEM HAVING ELECTROSTATIC CHARGE REDUCER Charles D. Erickson and George A. Ciotti, Erie, Pa., assignors to A. 0. Smith Corporation, Milwaukee, Wis. Filed June 17, 1969, Ser. No. 834,023 Int. Cl. B65d 87/48 U.S. Cl. 137-591 6 Claims ABSTRACT OF THE DISCLOSURE A flow system for petroleum products and the like. An unshrouded static charge reducer tube is connected in the storage means of the flow system for eliminating electrostatic charge resulting from liquid flow. The reducer is formed of a suitable plastic and a plurality of pins project inwardly into the internal flow passageway. A conductive member connects the pins to the storage means or some other element which defines a ground connection.

This invention relates to a flow system having a storage means and a static charge reducer means for eliminating the accumulated electrostatic charge resulting from the flow of the liquid through the system.

In the handling of flammable liquids such as petroleum products and the like, there is a severe danger of explosion and fire as a result of static electricity which accumulates in the liquids as a result of movement of the liquid through the passageway presenting a relatively static surface of a solid or another liquid. For example, explosions have occurred as a result of electrostatic accumulation arising during the transfer of liquid to tank trucks, railroad and ship storage means, blending and storage tanks as well as aircraft fueling tanks. In particular example, jet fuel and the like employed with aircraft is of necessity required to be a highly non-contaminated fuel. Generally, all airports include large filter tanks with filter stacks within the tanks through which all of the jet fuel is filtered to essentially remove all contaminates. The accumulated charge of the flowing liquid is a function of the flow rate and the static surfaces and consequently filters, as a result of the large surfaces presented to the liquid, are known to be a particularly substantial source of charge generation. Grounding of the tanks and other equipment provides for a partial solution in that the charge will transfer to the tank surface and drain off. However, the time element may be such that an explosion may be created before the charge has an opportunity to pass to ground. As a result, separate charge neutralizers or reducers have been connected directly in the line with an outer metal housing or shroud confining and directing the liquid through the neutralizer element. US. Pat. 3,141,113 suggests an alternative system wherein an insulating tube having a discharge pin is mounted as a separate series flow element. The pin is insulated from ground and connected to a preceding element which is a source of charge and which is also insulated from ground.

Generally, the prior art systems do present certain problems with respect to providing optimum protection and have certain disadvantages from the standpoint of interconnection to existing systems, particularly where underground flow systems are employed. For example, in existing airport installations employing filter tanks, an underground fiow system dispenses the liquid from the tank to one or more hydrants. Airports generally employ a hydrant distribution system and separate charge neutralizers are preferably provided underground immediately adjacent each hydrant. To excavate and provide the below groundinstallation of a reducer results in an installation cost of the reducer in excess of the equipment cost. Further, such systems require additional equipment which include sources of charge buildup in the liquid for transfer of the fuel from the hydrant to the airplane. Cart systems are generally employed where a movable cart is interconnected by a hose to the hydrant and then positioned adjacent the airplane for convenient transfer from the hydrant to the plane. It may then be advisable and generally is provided at the discharge end with a suitable contaminating material removing filter. This, however, is a new source of static charge. Although the charge may be minimized by reducing the fiow rate, an optimum system desirably permits relatively high flow rates.

BRIEF SUMMARY OF INVENTION The present invention is particularly directed to the provision of a small unshrouded static charge reducer mounted within a storage means forming part of the normal transfer equipment and in particular, connected to the inlet-outlet means of the storage means. In accordance with a particularly novel aspect of the present invention, the static charge reducer is formed as a tubular member of a suitable insulating material.

A plurality of pins are secured to the tubular member and project inwardly into the internal flow passageway defined by the tubular member. A conductive member connects the pins to the storage means or some other element which defines a ground connection.

The present invention appears to function as a result of creating a capacitive element of minimal capacitance and thereby generating an intensive voltage concentration, which can be controlled by proper pin placement. In the unshrouded flow line, the outer element of the capacitor is an apparent and undefinable plate, thereby creating an essentially indefinitely large separation. The basic capacitance equation defining capacitance states that the capacitance equals a materials dielectric constant times the plate area divided by the distance between the plates i.e., C=kA /d. The plate area and constant is defined by the reducer pipe. As a result of the separation distance, the capacitance is necessarily small. Further, the voltage across the chamber wall is defined by the equation V=Q/C, where V is the voltage, Q the charge and C the capacitance and for a small value of capacitance, the voltage is substantial. The large voltage results in an efiicient charge reducer and thus permits the use of relatively small units. At initial flow, the discharge is generally determined by the usual time constant of a capacitive system; i.e., the multiple of the capacitance times a resistance. In this application, the resistance of the liquid is the discharge resistance element. Thus, by establishing a minimal capacitance, the discharge time is also minimal and rapid charge reduction results.

Applicants have found that the use of a plurality of properly spaced pins create unusually satisfactory results. As previously described, applicants determined that the action of the unshrouded reducer arises from the high voltage generation. This feature is particularly apparent when a single pin is mounted adjacent to the entrance to the reducer. However, applicants also found that if the pin is placed too far from the entrance of the reducer, the device may actually overcompensate and introduce an opposite charge which would generally not be desirable except perhaps in some special instances. This may be avoided by moving of the initial pin upstream slightly toward the entrance.

The other downstream pins which remove any residual charge have been found to be advantageously grouped with the pins in each group equicircumferentially spaced about the reducer. Thus, two groups of three pins have been employed with highly satisfactory results. A very distinct advantage obtained with the submerged nonshrouded static charge reducer permits optimum positioning of the static charge reducer and in particular the location of the pins within the tubular member in proximity of the highest field concentration. This results in a substantially improved field distribtuion inside of the charge reducer with a resulting increased efiiciency.

The unshrouded tubular member is disposed within the storage means and interconnected drectly to the inlet and/ or the outlet depending upon the particular construction of the unit. This permits the removal of the charge at the very terminal point and minimizes the expense and cost of the construction of the static charge reducer as such. Furthermore, by employing the relatively small static charge reducer which is mounted and submerged within the liquid in a standard piece of equipment permits ready retrofit to existing flow systems.

In accordance with a particularly novel aspect of the present invention as applied to airport fueling systems and the like, the static charge reducer may be constructed generally in accordance with the individual filter elements employed in a filter tank. The static charge reducer is connected between the stack of filters and the related tank connecting conduit means to provide charge reduction and/or elimination at the very point of tank connection. Applicant has found that the submerged nonshrouded static charge reducer performs in an exceptionally satisfactory manner adjacent to the discharge and/or the inlet conduit connection of a tank.

The present invention has thus been found to provide a highly improved static charge reducing system which can be conveniently applied to existing systems as Well as to new systems and provides an exceptional degree of flexibility with respect to static charge reducing elements.

BRIEF DESCRIPTION OF DRAWING The drawing furnished herewith illustrates the best mode presently contemplated by the inventors for carrying out the subject invention in which the above advantages and features are clearly disclosed as well as others which will be readily understood from the following description of the illustrated embodiments.

In the drawing:

FIG. 1 is a pictorial view of a filter tank with parts broken away and sectioned to illustrate detail of construction of the embodiment of the present invention shown therein; I

FIG. 2 is a section through a static charge reducer shown in elevation in FIG. 1;

FIG. 2a is a. fragmnetary section taken generally on line 22 of FIG. 2;

FIG. 3 is a View of a compartmentalized tank body with various static charge reducer connections in the several corn artments; and

FIG. is a fragmentary view of an aircraft having an integrated static charge reducer in accordance with the teaching of the present invention.

DESCRIPTION OF PREFERRED ILLUSTRATIVE CONSTRUCTIONS Referring to the drawing and particularly to FIG. 1, the present invention is illustrated and applied to an airport fuel filtering unit which includes a vertically mounted storage tank 1 having a bottom inlet pipe 2 and an adjacent outlet pipe 3. The pipes 2 and 3 are laterally spaced and secured within the tank 1 and in slightly spaced relationship to the bottom wall 4 and includes a plurality of apertures 6 permitting the flowing liquid to flow from the inlet pipe 2 into the principal portion of the tank 1 and also to flow therefrom through the apertures 6 to the outlet pipe 3. A vertical dividing wall 7 extends between the bottom wall 4 and the distributing plate into an inlet chamber 8 and an outlet chamber 9 to which the pipes 2 and 3 are connected. A flanged conduit 10 is connected or integrally formed with the upper surface of plate 5 at each of the apertures 6 aligned with chamber 8 and project slightly upwardly to define a filter mounting element.

4 A stack of filters 11 are interconnected to each other and to a respective conduit 10. The stack of filters 11 project upwardly from the conduits 10. The filters 11 may be of any suitable construction such as tubular coalescer elements which remove the impurities as the liquid flows through the walls thereof. Thus, the incoming liquid flows inwardly through the inlet pipe 2 to the inlet chamber 8 and through the stack of filters 11 to remove any impurities. A similar stack of filters 12 is connected to similar flanged outlet conduits 13 aligned with each of the related apertures 6 in plate 5 to further filter the liquid as it is withdrawn from the tank (1.

In the embodiment of the invention illustrated in FIGS. 1 and 2, a tubular static charge reducer 14 generally corresponding in configuration to one of the filter elements 11 or 12 is interposed between the stack of filters 11 and the related conduits 10 and a similar reducer 15 is ll'IlOllIlii6d between the filters 12 and the outlet conduits 13.

In order to retain the same number of filters 11 and 12, the upper end of the tank 1 is extended upwardly by an extension ring 16 which is interconnected to the top of the tank 1 by a flange and bolt unit 17 and to the usual top cover 18 by a similar plurality of flange and bolt units 19. The conventional filter tan-k 1 includes a removable cover 18 and is readily fitted with the necessary extension to maintain the proper filter stack with the inserted reducers 1'3 and 15.

The static charge reducers 14 and 15 are similar completely unshrouded units, as shown in FIG. 2 and include a tubular body member 20 longitudinally aligned with the tubular filters 11 and 12 and secured in the stack including the adjacent conduit by any suitable means such as the conventional clamping members. The illustrated clamping members include hook bolts 21 hoo-ked beneath the flanged conduits 10 and '13 and over the top of the stack and connected by a turn buckle 22 adapted to draw them together, with similar clamping members at opposite sides of the stack to produce a balanced attachment.

The tubular body 20 of each static charge reducer is formed of an electrically insulating material such as polyethylene. A plurality of pointed electrode pins 23 extend through the wall of the tubular body and into the liquid flowing passageway through the static charge reducer and have a sharp pointed end. In the illustrated embodiment of the invention, each pin 23 is secured to the end of a mounting bolt 24 which in turn is threaded into a suitably threaded opening in the wall of the tubular member 20. The pins 23 are staggered about the tubular member 20 and particularly located to sense high field concentrations and thereby establish maximum efficiency. The pins 23 are, in a particularly novel aspect of the present invention, arranged with a single pin 23 adjacent but spaced from the entrance or downstream end 25 of the tubular body 20 and with circumferentially spaced pin groups axially spaced therefrom. In the illustrated embodiment, there are two groups of three pins each. In each group, the pins are axially aligned and equicircumferentially located to establish maximum spacing therebetween and a preferred distribution within the flow passageway to remove residual charge. The several pins 23 are interconnected by a common conductive Wire 26 to each other. The outer end of the common wire 26 is connected to the tank 1 as at 27. In turn, a ground connection 28 is provided to the tank 1 to particularly ground the pin system.

In the operation of the illustrated embodiment of the invention, the incoming liquid flows through the inlet chamber 8 and then upwardly through the conduits 10, the static charge reducers 1-4 and the stack of filters 11 into the filter tank 1. The liquid is Withdrawn from tank 1 through the filter elements 12, static charge reducers 15 at the bottom of each vertical stack of filters 12, outlet conduits 13, the chamber 9 and pipe 3. As the liquid flows through the static charge reducers 15, the charge created by flow through elements 12 is essentially completely removed as a result of the grounded pins 23. The liquid discharged through the discharge pipe 3 is therefore essen tially static charge free. Tests have shown that highly satisfactory charge removal results are obtained employing the relatively small unshrouded static charge reducer at the discharge end of a flowing liquid even without the inlet reducer 14 which has been illustrated to show the possibility of such use if desired.

The static charge reducer can, of course, be employed connected either to the inlet side or to the outlet side only of a storage system depending upon the particular application.

The flexibility and versatility of the present invention is more fully disclosed in the embodiment of FIG. 3 wherein the usual tank truck body 29 of a petroleum product tank truck is illustrated having a pair of dividers 30 defining three side-by-side chambers 31, 32 and 33 each of which is provided with a similar top loading hatch 34. The tank body 29 is grounded in the usual construction through a suitable ground means 35.

The first chamber 31 is illustrated with an L-shaped inlet conduit 36 connected to the body 29 and including a swivel connector 37 to permit rotation about a vertical axis. In the illustrated embodiment of the invention, the inlet conduit 36 is connected to an internal L-shaped conduit 38 secured overlying the inlet opening of the tank and extending laterally therefrom. A static charge reducer 39, constructed in accordance with the present invention, is secured to the end of the pipe 38 and projects laterally adjacent the bottom of the tank chamber 31. The static charge reducer 39 includes the plurality of pins 40 projecting inwardly into the static charge reducer passageway and a bonding wire 41 interconnecting the pins to each other and to the tank as at 42.

The chamber 31 is provided with an outlet sump 43 in the bottom of the tank. In the illustrated embodiment of the invention, the sump 43 is aligned with the terminal end of the static charge reducer 39 and includes an L-shaped outlet pipe 44 interconnected to the sump and including a suitable swivel connector 45.

In operation, the incoming liquid flows through the static charge reducer 39 into the chamber 31 to produce an essentially electrically neutral liquid within the storage tank. Further, if the liquid is transferred directly as it is introduced, the liquid will flow through the static charge reducer 39 and then directly through the outlet pipe 44 to transfer essentially electrically neutral liquid.

Chamber 32 is provided with a common inlet-outlet conduit 46. An internal conduit or pipe 47 is connected to the tank end of the common inlet-outlet conduit 46. The pipe 47 is generally an inverted J-shaped member which extends upwardly into the tank and then laterally and downwardly terminating in spaced relationship to the tank bottom of chamber 32. A static charge reducer 48 is connected to the terminal end of the pipe 47 and extends downwardly therefrom terminating within a sump 49. The bonding wire 50 again interconnects or grounds the static charge reducer 48 to the tank body. In the illustrated embodiment of the invention, the static charge reducer thus carries the liquid into the chamber 32 as well as from the chamber 32 to establish and maintain the liquid transferred with respect to the chamber 32 essentially electrically neutral.

In the above embodiments of the invention, the static charge reducer is formed as a relatively fixed component in an otherwise normally functioning tank-like unit. In chamber 33, liquid is supplied only through the top hatch opening 34 and is withdrawn through a bottom discharge sump 50a to which a discharge pipe 51 is connected through a suitable swivel connector 52. In accordance with another embodiment of the present invention, a separate inlet pipe 53, such as provided at a bulk loading station or the like, terminates in a static charge reducer 54 having a bonding wire 55 interconnecting the reducer 54 to the pipe 53. A ground connection 56 is made between the inlet pipe 53 and ground. In this embodiment of the invention, the incoming liquid passes through the terminal static charge reducer 54 which essentially neutralizes the liquid and thus establishes an electrically neutral liquid within the chamber 33. This liquid is subsequently withdrawn through the outlet pipe 51.

Still a further application of the present invention operating essentially in the same manner as the above embodiments is shown in FIG. 4.

In FIG. 4, a fragmentary portion of an aircraft 57 is illustrated containing a fuel tank 58 with an inlet conduit 59 terminating in the lower surface of the wing. In accordance with the embodiment of the invention shown in FIG. 4, a small static charge reducer 60 is connected to the inlet conduit '59 and within the fuel tank 58 and grounded to the wing 57. As a result, the liquid supplied to the tank 1 is neutralized to thereby further minimize danger of explosion and the like.

The various embodiments of the invention illustrated in'the drawing clearly indicate the tremendous flexibility and versatility of the small filter which can be directly incorporated into existing or new equipment in a relatively inexpensive manner. Furthermore, the unshrouded construction with the unrestricted placement of the reducer pins permits maximum efliciency. The invention thus provides a simple and improved means for static charge reduction in connection with flowing liquid transfer systems.

We claim:

1. In a flow system having a storage means with a liquid transfer means for transfer of liquid therethrough, the improvement in static charge reducer means to neutralize electrostatic charges in the liquid comprising, an unshrouded tubular member of an insulating material disposed within said storage means and defining a flow passageway connected to the transfer means with the corresponding liquid passing axially through the tubular member, a plurality of axially aligned and equicircumferentially spaced pins extending through the wall of the tubular member into the flow passageway to dispose the pins in contact with the liquid flowing in the tubular member, a single pin located adjacent the entrance of the tubular member, at least one group of said axially aligned and equicircumferentially spaced pins located upstream from said single pin, and conductive means connecting the pins to an electrically ground reference means.

2. The flow system of claim 1 wherein said group includes three pins.

3. In a flow system having a storage means with a liquid transfer means for transfer of liquid therethrough, said liquid transfer means having an inlet-outlet means, the improvement in the means to neutralize electrostatic charge within the liquid comprising, a static charge reducer means disposed within said storage means and having an insulating member defining a flow passageway connected to said transfer means to conduct the corresponding liquid and having pin means projecting into the flow passageway for removing the satic charge in said liquid transferred through the storage means, conductive means connecting the reducer means to an electrically ground reference means, a bottom depression in the storage means defining a sump adjacent said transfer means, a common conduit connected to said inlet-outlet means and extending upwardly into the storage means from the bottom of the storage means and then laterally and downwardly, said static charge reducer extending downwardly from the end of said conduit and terminating in said sump.

4. The flow system of claim 3 wherein said conduit includes an upper curved portion extending laterally and downwardly in alignment with said sump, said static charge reducer including a tubular member secured to the end of the conduit and extending downwardly from the end of said conduit and terminating adjacent said sump.

5. The flow system of claim 3 wherein said static charge reducer includes a tubular member extending downwardly from the end of said conduit and terminating in said sump having a pulrality of electrically isolated pins secured to the tubular member and projecting into the passageway, and said conductive means connecting said pins to said storage means, said storage means being a metal tank connected to a ground.

6. The flow system of claim 3 wherein said storage means includes a releasable opening, said transfer means includes a removable conduit adapted to extend through said opening into the storage means, said static charge reducer being secured to the end of said conduit and located within the storage means for transfer of liquid with respect to the storage means.

References Cited UNITED STATES PATENTS FRANK A. SPEAR, JR., Primary Examiner US. Cl. X.R. 

